Suggested troubleshooting:
1. Run Apple System Profiler (Apple Menu > About this Mac > More info)
See if the drive is recognized by the system (Is it in the profile under Hardware > Disk Burning)?
If it's not, it's either failed or the cable has disconnected.
2. If it is recognized by the system in step 1, try burning a disk through the Finder. If that works, it's a problem with iTunes. Sometimes, burning a disk in Finder cleans up the problems with iTunes. Alternatively, download a fresh copy of iTunes.
3. You can also try to reset the PRAM and open Firmware. You can get those instructions from searching the Apple website.
Hope these steps help.
David